The present invention generally relates to a tube pump for generating a pressure by pressing and deforming a tube. More particularly, the invention relates to an ink jet recording apparatus using the tube pump, which is capable of restoring an ink ejection capability of the print head by discharging ink from the print head by utilizing a negative pressure generated by the tube pump. Further, the invention relates to an ink jet recording apparatus which is provided with the tube pump as an ink supplier for supplying ink from a main tank (ink pack) to a sub-tank.
The ink jet recording apparatus is advantageous in that noise generated during the printing operation is low, and small print dots may be arrayed at high density. Because of those advantages, the ink jet recording apparatus has used for a variety of printings, mainly for color printing, recently. The ink jet recording apparatus is provided with an ink jet recording head which receives ink from an ink cartridge, and a paper feeder for moving a recording sheet relatively to the recording head. To print, the ink jet recording apparatus, while moving the recording head, causes the recording head to eject ink drops onto the recording sheet and forms ink dots thereon, in accordance with a print signal.
Thus, the ink jet recording apparatus must unavoidably handle with liquid ink. Accordingly, to prevent the clogging of the nozzle orifices, which is caused by filling of ink to the recording head and volatilization of ink solvent, a process to restore the ink-ejection capability of the recording head is carried out in which ink is forcibly sucked and discharged from the recording head. The forcible discharging of ink, which is performed for removing the nozzle clogging or when air bubbles are left in the recording head, is called a cleaning operation. The cleaning operation is carried out when the recording apparatus, which is not in use for a long time, is operated again, and when the user finds out poor print, such as blur of printed characters, and operates a cleaning switch.
In the cleaning operation, the following sequence of steps is carried out. The recording head is sealingly capped with a capping member, and a negative pressure is applied to the capped head to forcibly discharge ink, by sucking, into the capping member through the nozzle orifices of the recording head. The ink discharged into the capping member is sucked and sent to a used ink tank by the utilization of a negative pressure. Thereafter, the nozzle plate of the recording head is wiped out by a cleaning member formed with an elastic material, e.g., rubber.
A called tube pump has been used for the means for applying a negative pressure into the capping member since it is relatively simple in structure and easy to be reduced in size, and further does not soil the mechanism for sucking and discharging ink. The tube pump will be described in detail with reference to FIG. 31.
The tube pump 74 includes a pump frame 72, a pump wheel 70, and a pair of rollers 71a and 71b. The pump frame 72 has a tube support surface 76 arcuately defining a configuration of a flexible tube 75. The pump wheel 70 is rotated by a motive power transmitted from a drive member such as a sheet-feeding motor. A couple of roller support grooves 70a and 70b are disposed while being radially slanted between an axial direction and a circumferential direction of the pump wheel 70. The rollers 71a and 71b are rotatably mounted so that those are movable within and along the roller support grooves 70a and 70b, respectively.
A pair of guide members 73a and 73b, made of an elastic material, are disposed at positions facing the pump wheel 70 formed on the pump frame 72, while extending in the axial direction of the pump wheel 70.
L-shaped engaging grooves 72a and 72b are formed in the pump frame 72. The guide members 73a and 73b are planted in those engaging grooves 72a and 72b, respectively.
With such a structure, the guide members 73a and 73b guide respectively the rollers along the roller support grooves in the rotation backward direction, with rotation of the pump wheel. When the cylindrical body 42 is rotated in the forward direction (direction A), the rollers 71a and 71b are pushed back by the guide members 73a and 73b made of the elastic material, respectively. As a result, the rollers 71a and 71b, respectively, move in the outer circumference direction of the roller support grooves 70a and 70b, and the flexible tube 75 is compressed flat. Accordingly, a reliability of the pump driving operation is improved.
In the tube pump thus constructed, when the pump wheel 70 is rotated in the forward direction (direction A of an arrow), as shown in FIG. 31, the rollers 71a and 71b move in the outer circumference direction of the roller support grooves 70a and 70b. Those rollers rotate while pressing the flexible tube 75 flat. As a result, a pressure is generated in the tube and a negative pressure is applied to the capping member. Under the negative pressure, ink is forcibly discharged from the recording head, and the ink discharged into the capping member is sucked and sent to the used ink tank.
Conversely, when the pump wheel 70 is rotated in the reverse direction (direction B of an arrow), the rollers 71a and 71b move in the inner circumference direction of the roller support grooves 70a and 70b. As a result, the rollers are put in a release state in which the rollers are in slight contact with the tube. Accordingly, a trouble, e.g., clinging of the tube, is avoided.
The tube pump is used for restoring the ink-ejection capability to cause the recording head to discharge ink therefrom, and also for supplying ink from a main tank, which stores ink therein, to a sub-tank provided in the recording head.
The ink jet recording apparatus, which is used for office or business use, needs an ink cartridge of a large capacity since it handles a relatively large amount of printing. For this reason, a main tank as an ink cartridge (ink pack) is set to a cartridge holder, which is located on the side of the body of the recording apparatus.
The sub-tank is placed on the carriage on which the recording head is mounted. Ink is supplied from the main tank to the sub-tank via an ink supplying tube. Further, ink is supplied from the sub-tank to the recording head.
In this type of the ink jet recording apparatus, the tube pump is used as the ink supplier for supplying ink from the main tank to the sub-tank.
As described above, in the related tube pump, the roller rotates while successively pressing the tube flat. Through the operation, a pressure is generated within the tube to give rise to a negative pressure.
Accordingly, the tube being pressed flat by the rotating roller is restored to its original shape by an elasticity of the flexible tube per se (self-restoring ability).
The thickness (difference between the inner and outer diameters of the tube) of the flexible tube must be secured in a certain level. If the flexible tube is extremely thin, the restoring force is unsatisfactory, and a required suction force cannot be produced.
If the flexible tube is thick, the inner diameter of the tube is small, so that a predetermined quantity of suction cannot be secured. If the inner diameter of the flexible tube is set at a fixed value, the outer diameter is also large, and consequently the whole tube pump is large in size, and hence the ink jet recording apparatus itself is large in size.
Additionally, in the related tube pump, the tube pressed flat restores to its initial state by the elasticity (self-restoring ability) of the tube itself. In this respect, the material which may be used for the tube must be selected from among limited kinds of materials. The metal tube made of aluminum or the like has less elasticity, and hence cannot be used for the tube of the related tube pump.
The elasticity (self-restoring ability) of the tube per se serves as a reaction force when the tube is pressed flat. This results in increase of the pressing load, so that the pump efficiency is impaired.
Furthermore, extreme care must be exercised on the clinging of the tube since the tube being pressed flat is restored to its original state by the elasticity of the flexible tube per se (self-restoring ability).
For the background reasons mentioned above, the present invention has an object to provide a tube pump which is different in basic construction from the related tube pump, allows the use of a tube not having the self-restoring ability, and is small in size and high in pump efficiency. The invention has another object to provide an ink jet recording apparatus constructed using such a tube pump.
In order to achieve the above object, according to the present invention, there is provided a tube pump, comprising:
a drive shaft;
a rotor, fixed to the drive shaft so as to rotate therewith;
a tube pressing member, being swingable in an axial direction of the drive shaft;
a swinging member for swinging the tube pressing member in accordance with the rotation of the rotor;
a tube, an upper outer face of which is fixed to a lower portion of the tube pressing member;
a fixing member, to which a lower outer face of the tube is fixed,
wherein the tube is forcibly pressed and expanded in accordance with the swing motion of the tube pressing member, while the pressed/expanded part is shifted in an extending direction.
In this configuration, the tube is gradually pressed flat through a swing motion of the tube pressing member, and is returned to its original state. Accordingly, a tube having a small self-restoring ability or a low stiffness may be used for the tube. A thin tube may also be used. As a result, the size reduction of the tube pump is realized.
When the tube used is small in self-restoring ability or low in stiffness, a pressing load to the tube is lessened. Therefore, a tube pump of high pump efficiency is presented.
The term xe2x80x9cfixxe2x80x9d means a case where the tube is fastened to the tube pressing member, the tube fixing plate or the like by means of adhesion, and further welding, and further a case where the tube pressing plate or the like is formed integral with at least a part of the tube.
Preferably, the tube pressing member is provided as a plate member which is opposed to the rotor.
Preferably, the tube pump further comprises a spring member, for urging the fixing member toward the tube pressing member.
In this arrangement, the tube is pressed against the tube pressing member by the spring member. Therefore, when the rotor is made of a material having no elasticity, the tube is pressed flat at a fixed pressing force by the tube pressing member.
Here, it is preferable that the tube pump further comprises: a flange, formed at a lower end portion of the drive shaft, to which a lower end of the spring member is fixed; a plate member, to which an upper end of the spring member is fixed; and a ball bearing, provided between a lower face of the fixing member and an upper face of the plate member.
Preferably, the rotor is provided as a rotary disk member.
Here, it is preferable that the swinging member is provided as a ball body interposed between the rotary disk member and the tube pressing plate, so as to be movably fitted with a groove formed on an upper face of the tube pressing plate.
In this arrangement, a stable swinging motion of the tube pressing plate is secured.
Here, it is preferable that the groove is situated closer to the drive shaft than a cross sectional center of the tube.
In this arrangement, the pressing force of the tube pressing plate applied to the tube for pressing it flat is uniformly exerted on the tube, so that the tube is uniformly pressed to be closed. Therefore, there is no case where the tube is excessively pressed. The tube may be closed by a less amount of pressing and a less pressing load. This leads to reduction of the required drive torque of the pump, and hence presents a tube pump with high pump efficiency.
The lessening of the slanting of the tube pressing plate leads to the size reduction of the tube pump.
Here, it is preferable that the swinging member includes: a spring member, one end of which is fixed to the rotary disk member; a ball body, being movable on an upper face of the tube pressing plate; and a holder, to which the other end of the spring member is fixed, the holder for holding the ball body.
In this arrangement, the ball body is pressed against the tube pressing plate with the aid of the spring member. Accordingly, the tube pressing plate is swung at a fixed pressing force.
Alternatively, the rotor is provided as a rotary conical member.
Here, it is preferable that the swinging member is provided as a frustum body held by a side face of the rotary conical member, such that an axis of the frustum body is in parallel with a generatrix of the conical member.
Alternatively, the rotor is provided as a bar member, one end of which is fixed to the drive shaft.
Here, it is preferable that the swinging member is provided as a columnar body held by the bar member so as to be rotatable about an axis of the bar member.
Preferably, a through hole is formed at a center portion of the tube pressing plate, through which the drive shaft is inserted. The diameter of the through hole is larger than the diameter of the drive shaft. A cylindrical member is formed on a lower face of the tube pressing plate so as to surround the through hole.
In this arrangement, the tube pressing plate stably swings. When the swing of the tube pressing plate is large, the drive shaft sometimes comes in contact with the inner wall of the through hole of the tube pressing plate. In this case, the contact of the drive shaft with the tube pressing plate reduces the pump efficiency. Such a situation should be avoided as possible.
Preferably, the tube pressing plate is shaped into a hollowed cone so as to be swingable about a vertex of the cone.
In this arrangement, the tube pressing plate may be swing without providing the above described cylindrical member around the through hole.
Preferably, the tube pump further comprises a ball bearing interposed between the drive shaft and the tube pressing member.
In this arrangement, the drive shaft and the tube pressing plate are coupled with each other with the aid of a ball bearing, and the tube pressing plate is swing through the rotation of the drive shaft. Accordingly, the device construction is simplified.
Preferably, the tube is fixed to the tube pressing member and the fixing member by either adhesive or welding.
In this arrangement, the pressing/expanding operation can be stably performed, after the assembling.
Preferably, the tube pressing member, the tube and the fixing member are integrally formed.
In this arrangement, the assembling work may be omitted.
Preferably, the tube pressing member is provided with a hole for holding a projection formed on the upper outer face of the tube. The fixing member is provided with a hole for holding a projection formed on the lower outer face of the tube.
In this arrangement, it is easy to mount the tube to the tube pressing member and the fixing member. A stable pressing/expanding operation is secured.
Alternatively, the tube and the fixing member are integrally formed. A hook member is formed on the upper outer face of the tube, which is engaged with an engagement member formed on the lower portion of the tube pressing member.
Alternatively, the tube includes an upper tube part and a lower tube part, which are connected to form a tube. An upper face of the upper tube part and the tube pressing member are integrally formed. A lower face of the lower tube part and the fixing member is integrally formed.
The tube may be made of a material having a relatively low self-restoring ability, or a material having a relatively low stiffness.
An aluminum tube, an aluminum tube coated with resin or laminated with a resin layer, or a vinyl tube may be used for the tube.
Thus, a tube pressing load is lessened, and the tube pump of high pump efficiency is realized.
Preferably, the tube pressing member always presses at least a part of the tube.
In this arrangement, there is no case that the backward flow of ink occurs. If it is not always pressed, it is necessary to provide a check valve for blocking the backward flow of ink.
According to the present invention, an ink jet recording apparatus may use the thus constructed tube pump as a pump unit for sucking ink from the recording head. In this case, the size of apparatus is reduced and the suction operation is stably and highly efficiently performed.
According to the present invention, an ink jet recording apparatus may use the thus constructed tube pump as an inky supplier for supplying ink from the main tank to the sub-tank. In this case, the size of apparatus is reduced and the ink supplying operation is stably and highly efficiently performed.
According to the present invention, there is also provided a tube pump, comprising:
a pump shaft, provided as a fixed central shaft;
a tube, wound around the pump shaft, the tube being deformable in a radial direction of the pump shaft;
an inner cylindrical member, for surrounding the tube therein;
an outer cylindrical member, being rotatable around the pump shaft, while defining an annular passage between the inner cylindrical member; and
a ball body, provided in the annular passage while being movable therein in accordance with the rotation of the outer cylindrical member,
wherein the inner cylindrical member is eccentrically swung by the movement of the ball body, while deforming the tube.
In this arrangement, when the outer cylindrical member is rotated about the pump shaft, the ball body rolls in the circumference direction of the pump shaft while pressing the outer surface of the inner cylindrical member. With the rolling, the inner cylindrical member swings in a plane perpendicular to the pump shaft.
In this case, the tube is pressed in the tube winding radial direction at a position at which the inner surface of the inner cylindrical member is closest to the outer surface of the pump shaft. At a position where it is furthest from the outer surface of the pump shaft, the tube is returned to its initial state.
Accordingly, an elastic force of the tube per se is not needed for the restoring of the tube in shape. Because of this, a design strictness in selecting the inside and outer diameters of the tube is lessened, and the pump design is simplified.
The feature that the elastic force of the tube per se is not needed for the restoring of the tube in shape, implies that a material of the tube may be selected from among an increased variety of materials. In this sense, a design freedom is increased in selecting the tube. Accordingly, a metal material, e.g., aluminum, may be used as a tube material.
Additionally, the fact that the tube is able to resuming its initial state or shape through the swing motion of the inner cylindrical member implies that there is no need of using a material having a large self-restoring ability for the tube material. Accordingly, the pressing load is reduced and the pump efficiency is increased.
Further, the restoration of the tube to the initial state is performed through the swing motion of the inner cylindrical member. Therefore, there is no need of taking a measure for preventing a trouble caused by the tube clinging or the like, which inevitably occurs in the related technique. Also in this point, the pump design is simplified.
Preferably, grooves are formed on an inner face of the outer cylindrical member and an outer face of the inner cylindrical member, for guiding the movement of the ball body.
When the outer cylindrical member rotates, the ball body reliably rolls along the groove in the outer surface of the inner cylindrical member. A stable swing of the swing cylinder is secured.
Preferably, an inner peripheral portion of the tube is integrated with an outer face of the pump shaft. An outer peripheral portion of the tube is integrated with an inner face of the inner cylindrical member.
In order to the same advantageous effects, according to the present invention, there is also provided a tube pump, comprising:
a pump shaft, provided as a rotary central shaft;
an inner cylindrical member, for defining an annular passage between the pump shaft;
a tube, wound around the inner cylindrical member, the tube being deformable in a radial direction of the pump shaft;
an outer cylindrical member, being fixed with respect to the pump shaft, while surrounding the tube therein; and
a ball body, provided in the annular passage while being movable therein in accordance with the rotation of the pump shaft,
wherein the inner cylindrical member is eccentrically swung by the movement of the ball body, while deforming the tube.
In this arrangement, when the pump shaft is rotated, the ball body rolls in the circumference direction of the pump shaft while pressing the inner surface of the inner cylindrical member. With the rolling, the inner cylindrical member swings in a plane perpendicular to the pump shaft.
In this case, the tube is pressed in the tube winding radial direction at a position at which the inner surface of the inner cylindrical member is closest to the inner surface of the outer cylindrical member. At a position where it is furthest from the inner surface of the outer cylindrical member, the tube is restored to its initial state or shape.
Preferably, grooves are formed on an inner face of the inner cylindrical member and an outer face of the pump shaft, for guiding the movement of the ball body.
Preferably, an inner peripheral portion of the tube is integrated with an outer face of the inner cylindrical member. An outer peripheral portion of the tube is integrated with an inner face of the outer cylindrical member.
In order to attain the same advantageous effects, according to the present invention, there is also provided a tube pump, comprising:
a pump shaft, provided as a fixed central shaft;
a first cylindrical member, being rotatable around the pump shaft;
a second cylindrical member, for defining an annular passage between the first cylindrical member;
a tube, wound around the second cylindrical member, the tube being deformable in a radial direction of the pump shaft;
a third cylindrical member, being fixed with respect to the pump shaft while surrounding the tube therein; and
a ball body, provided in the annular passage while being movable therein in accordance with the rotation of the first cylindrical member,
wherein the second cylindrical member is eccentrically swung by the movement of the ball body, while deforming the tube.
In this arrangement, when the pump shaft rotates, then the ball body rolls in the circumference direction of the pump shaft while pressing the inner surface of the second cylindrical member. With the rolling, the second cylindrical member swings in a plane perpendicular to the pump shaft.
In this case, the tube is pressed in the tube winding radial direction at a position at which the outer surface of the swing cylinder is closest to the inner surface of the third cylindrical member. At a position where it is furthest from the inner surface of the third cylindrical member, the tube is restored to its initial state or shape.
Preferably, grooves are formed on an inner face of the second cylindrical member and an outer face of the first cylindrical member, for guiding the movement of the ball body.
Preferably, an inner peripheral portion of the tube is integrated with an outer face of the second cylindrical member. An outer peripheral portion of the tube is integrated with an inner face of the third cylindrical member.
In the above tube pumps, it is preferable that the tube is taken out in an axial direction of the pump shaft.
In this arrangement, the take-out portion of the tube may be disposed at the pump shaft (fixed rotation center) or the fixed cylindrical member when the pump is assembled.
Alternatively, the tube is taken out in the radial direction of the pump shaft.
In this arrangement, the take-out portion of the tube may be disposed at a position as viewed in the radial direction of the fixed cylindrical member.
Preferably, the ball body always presses at least a part of the tube.
In this arrangement, there is no case that the backward flow of ink occurs if it is not always pressed, it is necessary to provide a check valve for blocking the backward flow of ink.
Preferably, the tube is made of a material having a relatively low self-restoring ability, or a metal having a stiffness which is deformable by the ball body.
In this arrangement, the pressing load to the tube is lessened, and the pump efficiency is increased.
An aluminum tube, an aluminum tube coated with resin or laminated with a resin layer, or a vinyl tube may be used for the tube.
Preferably, a friction resistance of an inner surface of the tube is larger than a friction resistance of an outer surface of the tube.
In this arrangement, fluid (air) smoothly flows within the tube.
Preferably, the tube is interposed through use of either adhesive or welding.
In this arrangement, the tube, the swung cylindrical member and the pump shaft or the fixed cylindrical member are firmly coupled.
According to the present invention, an ink jet recording apparatus may use the thus constructed tube pump as a pump unit for sucking ink from the recording head. In this case, the pump design is simple, and a design freedom is increased in selecting the tube, and the pump efficiency is improved.
According to the present invention, an ink jet recording apparatus may use the thus constructed tube pump as an inky supplier for supplying ink from the main tank to the sub-tank. In this case, the pump design is simple, and a design freedom is increased in selecting the tube, and the pump efficiency is improved.